I bought a monitor since the smarts in my smart-tv died, making the entire display unusable. Now I wanted to use a separate SBC for smarts in the "dumb" monitor. I would have gone for a modded fire-stick, but Amazon in their infinite wisdom, sunset all versions except the 720p potato and the smart-speaker-cube. I'm currently using a RaspberryPi 4 and looking at argon one for a remote control case. Googles widevine does limit the DRM on some content I "own" though. With Amazon on course to EOL the more sane sticks, are there any well-moddable streaming-sticks/boxes, that bring the relevant codecs and DRMs?
If you just don’t like ads AppleTV works great.
That said if you’re set on something less locked down you might look into Dune-HD boxes. They have some that have a dual OS. One is Android TV (not sure how mod-able) the other is Linux that can have other kinds of apps. They’re virtualized and accessible without a reboot. They have great codec support. Just realize only some of their models have the Android TV dual system thing.